Windows 7 Compatibility Mode makes game run as windowed

Hi, Recently i have tried using D3DOverrider in skyrim, but it seems that if i try to run it as windows 7 compatibility mode, it forces the game to run windowed (not aero windowed, but basic mode). I have tried changing the game's settings, pressing alt enter, ctrl enter, windows key F, nothing forces fullscreen. And to run D3Doverrider, i have to run the program as windows 7 compatibility...